Collecting, storing, and conditioning plant embryos, especially somatic embryos, prior to germination are key processes in many aspects of the agriculture industry. The activities necessary for performing these processes, however, are usually performed by hand. For instance, individual embryos are typically transferred to and from various media and vessels and must be plated onto gel media, one by one using forceps and often with the guidance of a dissecting microscope.
Such “hand harvesting” methods are burdensome, time-consuming, costly, and susceptible to contamination. Not only that, but only a limited number of embryos can be collected and treated by a single person during a given period of time. Accordingly, any attempt to increase the number of embryos that can be harvested and subsequently conditioned for germination necessarily requires an increase in manpower, which itself can be costly and often impractical.
An added concern is the inclusion of polyethylene glycol in embryo development media as a osmotic agent. Polyethylene glycol has been incorporated into various media to boost embryogenic development because it is thought to help trigger embryo development. See Fowke et al., Somatic Cell Genetics and Molecular Genetics of Trees, Quebec City, Canada, Aug. 12-16, 1997, which is incorporated herein by reference.
A problem with polyethylene glycol, however, is that it adheres to embryos, possibly interfering with embryo germination. Traditionally, removal of polyethylene glycol is accomplished by storing polyethylene glycol (PEG)-treated embryos on a gel medium without PEG in the cold for a number of weeks. The polyethylene glycol eventually diffuses into the medium away from the embryos. Not surprisingly, this is a time-consuming and burdensome treatment and removal strategy, which imparts an oftentimes unacceptable delay in the overall harvesting and conditioning process.
The agricultural industry and, in particular, the forestry sciences, therefore, are faced with a laborious, expensive, and inefficient method for making, gathering and preparing plant embryos. Such factors prove to be obstacles when operating at commercial levels. And still, hand harvesting is a typically routine practice.
As explained below, however, the present invention provides a robust “Mass Harvesting” method that is rapid and inexpensive. Since Mass Harvesting (MH) minimizes human intervention, it is less susceptible to contamination. Furthermore, the present invention also provides a new way for removing polyethylene glycol. Moreover, the Mass Harvesting method is highly efficient, allowing the simultaneous collection of thousands and hundreds of thousands of plant embryos during a period of time, and can be readily scaled-up for commercial purposes.
In this respect, the present invention also provides a combinatorial approach to exploiting and optimizing genotype-by-treatment interactions of multiple steps in the somatic embryogenesis process.